Splinter Cell On TV
During the 4th mission The Penthouse, when you get near the spiral staircase, there will be a TV which has Splinter Cell showing.

Halo
This is something that is quite amusing. When you go to write a text message on Xbox Live, if you enter the word "Halo", it gives you a message saying offensive text, cannot be sent. Just another of many cracks on video games to be found in Splinter Cell: Chaos Theory.

Cameras In The Dark
Cameras that do not use thermographic vision can be be fooled by shooting out all the ambient and direct light sources to darken the area. As long as the light meter is completely dark, these normal cameras cannot see your spy.

Half-Life
In the Battery mission when you need to crack the casing on the missile launcher Sam says that he didn't bring a crowbar. Then Grimsdottir says "Whatever. Crowbars are for geeky video game characters.", a reference to Gordon Freeman from Half-Life and Half-Life 2.

Prince of Persia
During Stage 5, while infiltrating Displace International, Sam will come across two guards talking about Prince of Persia Warrior Within. It is the small cafe next to a laser filled hallway, past a keypad locked door. A second way to access the room is through a vent. Because Sam is inside the vent, the conversation becomes difficult to hear

Hokkaido Milan Nedich Objecitve
Inspect the two SUVs' license plates either remotely (through Fisher's binoculars) or by interacting with them up close. Redding sheds some light on the real Milan Nedich.

Displace International Milan Nedich Objective
Laser mic and record (by zooming in with the EEV) the conversation on the third floor when a merc is assigned to the penthouse by an executive (the room is first one on your right when you get off the elevators on the third floor). Aim the EEV (binoculars) at the glass. This is the ONLY way to get credit for listening to the conversation.

Whacking North Korean UAVs
North Korean UAVs are tough to take down, but they can be avoided. However, if you went with a kit with a sniper attachment, you can take them out with one well placed shot (anywhere on the body).

Stopping The Missile Launch
In the final section of the DPRK missile base, Fisher has 3 minutes to stop the missile. From where the missile launches, head right and down into the door to the command center. The abort codes are on the PC to the right of that door. The codes must then be entered in one of the missile command center's PCs, which are the two rooms near the large elevator (lift) leading to the base commander's office on the level above. Assuming you took out all the enemies in that area, the three minutes are more than enough time to abort the missile.

Stick Camera Reuse
Sticky cameras may be reused in almost any mode as long as they are not destroyed by gunfire or did not use their gas attack.

Elite Mode
Successfully complete Story Mode to unlock Elite Mode, where you only have a knife to use.

Metal Gear Solid
During the final mission, at the escalator where there are 3 guards talking at the bottom of it...wait at the top of the escalator and one of the guards will be begin walking up to your level. Grab him and interrogate him to hear him make a crack about Metal Gear Solid.

Unlock Elite Mode
Unlock Elite mode in co-operative play by clearing co-op story mode. Elite mode basically starts both spies off with no ammo for the SC-20K or the SC pistol, except for the ammunition you may find in the levels. Time to work that knife.

Tank Movement
The tanks you face in Solo Mode are rather tough but they move in preset patterns. Down the gunner sitting in the turret, then watch the tank's gun. When it aims away, that's your cue to move by or above it. The only way to destroy a tank is to throw a frag grenade into the gunner's hatch. Quicksave to make sure you don't squander your grenades.